Report: NREL Liquid Cooled Server Experiments with Opticool

Wednesday, January 17th, 2024

Results for Liquid Submerged Server Experiments at NREL’s Advanced HVAC Systems Laboratory

Eric Kozubal
National Renewable Energy Laboratory


The author would like to recognize the following efforts and people from NREL for their assistance in this

  • The Wells Fargo Innovation Incubator (IN2) program for funding the project through a competitive selection process,
  • James Shelby who installed the operating systems and PTU software, and created scripts to operate and collect data on the servers,
  • David Sickinger who provided insight into the operation of liquid cooled data centers and assisted in the experimental design,
  • Kevin Regimbal who provided guidance and insight to the operation of liquid cooled data centers, and
  • Report reviewers: David Sickinger, Jennifer Scheib, Kate Cheesbrough, Shanti Pless, and Otto VanGeet

The IN2 program would like to thank the following organizations for supporting the project by donating components and materials used in the LiquidCool Solutions LSS system:

  • Intel Corporation for providing Xeon processors
  • Micron Technology for providing server memory
  • DSI Ventures for providing the dielectric coolant

Personnel from Intel Corporation also reviewed the content of this report


Executive Summary

LiquidCool Solutions (LCS) has developed liquid submerged server (LSS) technology that changes the manner in which computer electronics are cooled. The technology provides an option to cool electronics by the direct contact flow of dielectric fluid (coolant) into a sealed enclosure housing all the electronics of a single server. The intimate dielectric fluid contact with electronics improves the effectiveness of heat removal from the electronics. The LSS technology has the following advantages over traditional aircooled server systems:

  1. Maintains a small difference between central processing unit (CPU) and memory temperatures and inlet coolant temperature, allowing for:
      1. Use of higher temperature coolant
      2. Higher temperature heat recovery
      3. Ability to maintain lower electronic temperatures
  2. Eliminates the parasitic cooling energy used by fans
  3. Lower capital and energy costs in a building that contains a data center because the heat
    removed from the servers can:

    1. More effectively be rejected to ambient using lower cost systems
    2. Be re-used effectively as a heating source for the building.

The LSS shown in Figure 1 is encased in a liquid tight aluminum housing and was outfitted with two
windows such that the internal electronics and motherboard are visible.